Class QueryResult

java.lang.Object

org.projog.api.QueryResult

public final class QueryResult
extends Object

Represents an executing query.

Field Summary

Fields

Modifier and Type	Field	Description
private boolean	hasBeenEvaluated
private boolean	hasFailed
private final Predicate	predicate
private final Map<String,Variable>	variables

Constructor Summary

Constructors

Constructor	Description
QueryResult(PredicateFactory predicateFactory, Term query, Map<String,Variable> variables)	Evaluates a query.

Method Summary

Modifier and Type	Method	Description
private boolean	evaluate()
String	getAtomName(String variableId)	Returns the name of the atom instantiated to the variable with the specified id.
double	getDouble(String variableId)	Returns the double value instantiated to the variable with the specified id.
long	getLong(String variableId)	Returns the long value instantiated to the variable with the specified id.
Term	getTerm(String variableId)	Returns the term instantiated to the variable with the specified id.
Set<String>	getVariableIds()	Returns id's of all variables defined in the query this object represents.
boolean	isExhausted()	Returns true if it is known that all possible solutions have been found, else false.
boolean	next()	Attempts to evaluate the query this object represents.

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

predicate

private final Predicate predicate

variables

private final Map<String,Variable> variables

hasBeenEvaluated

private boolean hasBeenEvaluated

hasFailed

private boolean hasFailed

Constructor Details

QueryResult

QueryResult(PredicateFactory predicateFactory,
 Term query,
 Map<String,Variable> variables)

Evaluates a query.

Parameters:

query - represents the query statement being evaluated

variables - collection of variables contained in the query (keyed by variable id)

PredicateFactory - the PredicateFactory that will be used to evaluate the query

See Also:

• QueryStatement.executeQuery()

Method Details

next

public boolean next()

Attempts to evaluate the query this object represents.

Subsequent calls of the next() method attempt to reevaluate the query, and because it returns false when the are no more results, it can be used in a while loop to iterate through all the results.

Returns:

true if the query was (re)evaluated successfully or false if there are no more results. Once false has been returned by next() the next() method should no longer be called on that object.

Throws:

ProjogException - if an error occurs while evaluating the query

evaluate

private boolean evaluate()

isExhausted

public boolean isExhausted()

Returns true if it is known that all possible solutions have been found, else false.

Returns:

true if it is known that all possible solutions have been found, else false.

See Also:

• Predicate.couldReevaluationSucceed()

getAtomName

public String getAtomName(String variableId)

Returns the name of the atom instantiated to the variable with the specified id.

Parameters:

variableId - the id of the variable from which to return the instantiated term

Returns:

the name of the atom instantiated to the variable with the specified id

Throws:

ProjogException - if no variable with the specified id exists in the query this object represents, or if the term instantiated to the variable is not an atom

See Also:

• getTerm(String)

getDouble

public double getDouble(String variableId)

Returns the double value instantiated to the variable with the specified id.

Parameters:

variableId - the id of the variable from which to return the instantiated term

Returns:

the name of the atom instantiated to the variable with the specified id

Throws:

ProjogException - if no variable with the specified id exists in the query this object represents, or if the term instantiated to the variable is not a number

See Also:

• getTerm(String)

getLong

public long getLong(String variableId)

Returns the long value instantiated to the variable with the specified id.

Parameters:

variableId - the id of the variable from which to return the instantiated term

Returns:

the value instantiated to the variable with the specified id

Throws:

ProjogException - if no variable with the specified id exists in the query this object represents, or if the term instantiated to the variable is not a number

See Also:

• getTerm(String)

getTerm

public Term getTerm(String variableId)

Returns the term instantiated to the variable with the specified id.

next() must be called before this method.

Parameters:

variableId - the id of the variable from which to return the instantiated term

Returns:

the term instantiated to the variable with the specified id (or the Variable of representing the variable if it is uninstantiated)

Throws:

ProjogException - if no variable with the specified id exists in the query this object represents

See Also:

• getAtomName(String)
• getDouble(String)
• getLong(String)

getVariableIds

public Set<String> getVariableIds()

Returns id's of all variables defined in the query this object represents.

Returns:

id's of all variables defined in the query this object represents